Process and device for automatic verification of the positioning of a surgical instrument

Abstract

Process and device for use in surgery comprising a conducting element capable of shifting from a first medium to a second medium, which can measure an electrical parameter such as conductance and which can present a variation threshold during its movement when the conducting element is in contact with the second medium. The device can determine the variation of the electrical parameter during the movement of the conducting element in the first medium, as well as detect at least one predefined critical value and produce a signal when this critical value is detected.

I claim: 
     
       1. Device for use in surgery comprising a conducting element adapted to be displaced in a first medium, towards a second medium, further comprising means for measuring an electrical parameter; said device presenting a variation threshold, during said displacement, when said conducting element is in contact with said second medium, said device further comprising means for detecting at least one predetermined critical value of said electrical parameter and means for producing a signal when said determined value attains said critical value, wherein said device further comprises: means for determining the drift, or slope, of said electrical parameter, along displacement of said conducting element in said first medium.   
     
     
       2. Device according to claim 1, wherein said device comprises means for storing the value of the maximum drift, or slope, of said electrical parameter, during said displacement of said conducting element, and further comprising analysis means for determining the critical value of said electrical parameter from said value of the maximum drift or slope. 
     
     
       3. Device according to claim 2, wherein said critical value is substantially equal to half the value of said maximum drift, or slope. 
     
     
       4. Device according to claim 1, wherein said conducting element comprises a tool, said device comprising an ultrasound generator which vibrates said tool, said device further comprising servo-control means controlling the operational parameters of said tool, said parameters being one or more of amplitude and vibration frequency, said servo-control means being adapted, when the value of said drift or slope of said electrical parameter attains said critical value, to modify said operational parameters of said tool as a predetermined function of time. 
     
     
       5. Process for detecting the apex of a tooth comprising the steps: introducing an element conducting electric current in the radicular canal of said tooth, said conducting element being displaced in said radicular canal towards said apex of said tooth,   measuring an electric parameter which presents a variation threshold when said conducting element lies at the apex of said tooth during said displacement,   determining the drift, or slope, of said electric parameter along said displacement of said conducting element, and   producing a signal when the value of said drift, or slope, attains a predetermined critical value.   
     
     
       6. Process according to claim 5, wherein samples of said measured values of said electric parameter are taken, said samples being used to produce a smoothed curve representing the variations of said electrical parameter as a function of the displacement of said conducting element. 
     
     
       7. Process according to claim 6, wherein the frequency of said samples is increased when said drift, or slope, of said smoothed curve attains a value close to said critical value. 
     
     
       8. Process according to claim 5, wherein said critical value is determined from the measurement of the maximum drift, or slope of said smoothed curve. 
     
     
       9. Process according to claim 5, wherein said element is a vibrating tool, said tool machining the walls of said radicular canal, the operational parameters of the vibration of said tool being modified as a predetermined function of time when said drift, or slope, of said electrical parameter attains said critical value. 
     
     
       10. Process according to claim 9, wherein said modification of said operational parameters results in complete stoppage of the vibration of said tool.